Air conditioning system



Dec. s, 1942. w. L. MGGRATH v 2,304,269

AIR CONDITIONING SYSTEM Filed llay 14, 1938 William Lucerna PatentedDec. 8, 1942 AIB. CONDITIONING SYSTEM william r.. McGrath, si. raul,Minn., signor to Minneapolis-Honeywell Regulator Company, Minneapolis,Minn., a corporation of Delaware Application may 14, 193s, serial No.zoaoss (c1. sz-i 7 Claims.

This invention relates to an air conditioning system and moreparticularly to asystem wherein sensible and latent heat is removed fromair which is circulated through a space according to the requirements ofthe space.`

In accordance with my invention air eration system, the air then beingcirculated through the room or space to be conditioned. A compressorrunning at constant speed supplies refrigerant to the evaporatorcoils'and the iiow of refrigerant to each of the coils is controlled bysuitable valve means. When the temperature of the space is above adesired value and the humidity is at or below a desired value,refrigerant is supplied to both of the evaporator coils. Should thehumidity rise to an undesirable value, the flow of refrigerant to one ofthe evaporator coils is interrupted with the result that the temperatureof the other evaporator coil will be lower than the temperature of thecoils when refrigerant is iiowing through both of the coils. This isdesirable since less heat must be removed from the air in order toeilect a reduction in temperature of the air than is necessary whendehumidication is required, since in order to reduce the temperature itis necessary only to remove sensible heat from the air whereas whendehumidification is required, both sensible and latent heat must beremoved from the air. The coils are so arranged that a'portion of theair passes over one 'coil and another portion of the air passes over theother coil so that when one coil only is being utilized fordehumidiiication some of the air passing through the chamber willby-pass this coil and may be utilized for reheating the air. Means arealso 'provided for supplying refrigerant to both of the coils should thetemperature in the space `become excessively high regardless of thehumidity in the space in order that amaximum amount of sensible coolingmay take place. It is therefore an object of my invention to provide anovel control means for the evaporator coils of a refrigeration systemwherein these coils are used to control the temperature andhumidityconditions within a space to be conditioned.

Other yobjectswill become apparent-upon a study of the specification,claims, and appended drawing, the single figure of which illustratesdiagrammaticallyrone form of my invention.

Referring more particularly to the drawing, an air conditioning chamber,is represented by the reference character I0. .This chamber may includea fresh air inlet a return air inlet I2,

is circulated over a pair of evaporator coils of a refrigfor circulatingair through the chamber I0 and a space I6 to be conditioned. Dampers |1and il may be provided in the fresh and return air inlets, respectively,for controlling the proportions of fresh and return air admitted to thechamber I0. These dampers may be manually operated or automaticallyoperated in any suitable manner.

Mounted within the chamber I0 and transversely arranged with respect toone another are a pair of evaporators and 2|. A compressor 22 driven bya motor 23 is provided for supplying refrigerant to the evaporator coils2D and 2|. The high pressure side of the compressor 22 is connected bymeans of a pipe 26 with a condenser 21. A pipe 28 connected to theoutlet of the condenser 21 leads the refrigerant to a pair of valves 30and 3|. The outlet of valve 30 communicates with the inlet of theevaporator 20 by means of a pipe 33 and a second pipe 34 leadsrefrigerant from the outlet of valve 3| to the inthe outlets ofevaporators 20 and 2|, respectivean outlet I3, and a 4fan I4 driven by amotor 65 ly, and communicate with a pipe 42 leading to the inlet of thecompressor 22. In the operation of the refrigerating apparatus therefrigerant is compressed by the compressor 22, is condensed b3 thecondenser 21, and then iiows into the coils 2|| and 2| providing thevalves 22 and 3| are open, where the refrigerant is evaporated, the flowof 4refrigerant into the evaporators also being controlled by the`expansion valves, the refrigerant being evaporated inthe evaporatorsand absorbing heat from the air passing thereover and the evaporatedrefrigerant then flowing back to the compressor 22.

For controlling the operation of the `compressor I have illustrated asuction pressure controller 45. This controller may include anexpansible bellows 45 connected by means of a pipe 41 to the pipe 42leading to the inlet of the compresser. A lever 45 pivoted at 45 isbiased by means of a spring 5|! into engagement with the upper portion'of the bellows. Lever 48 carries a mercury switch 52 of conventionalconstruction and when the pressure on the suction side of the compressordrops to a low enough value, the bellows 45 contracts and a lever 4l ismoved under Line wires 53 and 54 may be connected to a suit- The ilow ofvrefrigerant being of any conventional y following circuit: from`conductors 56, mercury f motor 23, and conductor moves across thepotentiometer justable resistance ance Y 661s connected by able sourceof power (not shown) and are provided for supplying` energyto the motor23 as well as to the positioning means for the valves 36 and 3| as willbe henceforth explained. Power is supplied to the motor 23 when thesuction pressure onvthe suction side of the compressor is above apredetermined low value through the the line wire 53 through switch 52,conductor 51, 56 to the line 56. It will nowbe clear that whenthe'suction pressure drops to a low enough value this circuit to themotor 23 will be interrupted by the contraction of the bellows 46. Y

The positions oi valves 36 and 3| may be controlled by suitable means 66and 6| which may be in the form of solenoids having an armature suitablyconnected to the valves. Energization of the solenoids causes the valvesto open positions and upon deenergization of the solenoids the valvesmay be moved to closed positions under the influence 'oi' gravity or asuitable biasing means (not shown).

Mounted within the space to be conditioned is a thermostat indicatedgenerally by the reference character 66. This thermostat mayinclude abimetallic element 65 and an arm 66 carried thereby and engaging aresistance 61 across which the arm 66 sweeps in response to variationsin temperature in the space |6, the arm moving to the rightin responseto an increase in temperature and to the left upon a decrease intemperature. 'Ihe l.arm 66 and resistance 61 form a controlpotentiometer i'or a motor 68. This motor may be a proportioning motorof the type illustrated in Patent No. 2,028,110 issued to D. G. Tayloron January 14, 1936. 'Ihe terminals 66 and 16 of the motor are connectedt0 the extremities oi' resistance 61 by means of conductors 1|' and 12,respectively. The terminal 16 is connected to the arm 66 of thethermostat 66 by means of conductors 13, '|6 and the center tappedresistance 15. Power is supplied to the motor by means oi.' wires 18 and19 connected to a suitable source oi.' power will be v*understoodA upona study of the above mentioned Taylor' patent that as the arm 66 61, theshaft 86 (not shown). It

to be moved Y l the arm 66 will have to move to A upon movement of thecontrol range of the arm 66 will be shifted to wise'the cam |6| operatesa switch arm driven by the motor 68 will rotate an amount i which isproportional to the extent oi'movement.

of the arm 66 with the resistance 61.

Also connected to the center terminals 16 of the motor 68 by' means ofconductors 13, 82, ad-

83, and .conductor 6 6 is the control arm 65 oi' a second potentiometer.The

A arm 65 forms one arm 'of a bell crank lever pivoted at 66, the otherarm 81vthereoi being biased by mea oi' spring 68 with of the ows 69. Thebellows 86 is connected by means of a capillary tube 96 toa bulb 8|, thetube, bulb, and bellows being lled with a suitable volatile iluid. Thebulb 6| may be positioned outdoors so that the bellows 86 will expandand contract in' response to variations in outdoor temperature. It willbe apparent that as the bellows expands and contracts the ann'65 will becaused to move over the resistance 66. Upon an increase in outdoortemperature the arm 65 will moveY to the of conductors 86 and 1| withthe terminal 66 oi the motor 68 and the opposite end of the resistmeansof conductors the upper portion' vclockwise direction arm Vther movementof the arm 66 to arm |66 will b'e moved into engagement with si and 12with the motor terminal 1o. ii; win now be seen that the potentiometers66 and 61 are connected in parallel to the motor cause movement of theshaft 86 of the motor 66.

By reason of the adjustable resistance 83 interposed in the circuit tothe arm'85 this arm will have less effect on the motor for a givenmovearm 85 with respect to resistance 66 has theeilect of shifting thecontrol range of the arm 66 with respect to the resistance 61 arm 85moves to the right for example in respouse to anV increase in outdoorthe right in order to cause the motor to return position so that thecontrol range of will move to the right in response to a movement oi thearm 85 tothe right and likewise arm 85 to the left the the arm 66 theleft. The provision oi the-center tapped resistance insures that thecontrol range X of the arm 66 will have the same magnitude regardless ofthe position of this control. range. k

Carried by the shaft 86 are a pair of cams |66 and |6|. Operated by thecam |66 is a switch arm |62 which engages a iixed contact |63 uponmovement of the cam to a position wherein the arm |62 is moved upwardly.Like- |66 which cooperates with a xed contact |65. These cams are soarranged that as the cams rotate in a |62 willilrst be moved intoengagement with the contact |66 and subsequently the arm 66 will bemoved into engagement with the contact |615. As the arm 66 moves towardsthe right the cams |66 and 6| are rotated in a clockwise direction bythe motor 66 through an amount which is proportional to this arm. As thearm 66 movestoward the right in response to an increase in .thetemperature of the space the arm |62 will first be moved by the cam '|66ment with the switch contact |63 into engagethe right the the iixedcontact |65. 'I'he temperatures at which the arms engage theirrespective contacts will depend upon the position of the control range Xof the arm 66 oi' thermostat 66 and since this in turn depends upon theoutdoor temperature it will be seen that as the-outdoor temperaturerises the temperature at which the arms engage their respective contactswill be corre- 4 Spondinsly higher.

Also moimted within the space is is a humidity responsive device 6 whichmay be of any suitable construction and is shown as comprising ahumidity responsive element lH-iixed at one end as at 2 and h'aving itsopposite end connected to a lever ||3 pivoted at ||6 and biased upwardlyby means vfiof'a spring H5. Carried by the lever |8 is a mercury switch|26, this switch including contacts |2|, |22, |23, and |26 and a mercuryelement |25. When the humidityis low the switch will be tilted in theposition illustrated and 68 and accordingly movement of either arm or 66with respect to the corresponding resistances will so that as thetemperature Y to its initial 2,304,269 comme m and m wm be connected by'me mercury element |20. Upon an increase in relative humidity theelement will expand and orator coil, so that the air being circulatedVthrough the chamber I is not cooled thereby. 1

Should now the temperature inthe space increase to a high enough value,the arm |02 will be moved by cam |00 into engagement with' contact |00since the movement of arm 00 of thermostat 00 to the right in responseto an increase in temperature will cause shaft 00 to rotate the cam |00in a-clockwise direction. The solenoids 00 and 0| will now be energizedas follows, it being assumed that the humidity in the space has notrisen to a sufllciently high valuel to tilt the switch |20 in theopposite direction. Current ilow-s through' the solenoid 00 as follows:from line 00 through conductor |00,v contact |00, switch arm |02,conductor |0|, contacts |20 and |20 of switch |20, conductors |00, |00to the solenoid 00 and conductors |00 and |01 to the line 00. Currentiiows through the solenoid 6| as follows: from line 00 through conductor|00, contact |00, switch arm |02, conductor |00, solenoid 0|, andconductors |00 and |01 to. the line 00.l Thus upon a rise in temperatureto a certain value both valves 00 and 0| are open providing the humidityin the space is relatively low so that refrigerant is now supplied underthe control of the expansion valves 00A and 01 to the evaporatcrs 20 and2| Vwhereby a reduction in' temperature of the air passing through thechamber l0 is effected.

Assume now that the temperature is high and that the humidity inthespace reaches an undesirable value and that switch |20 is tilted inthe opposite direction wherein the circuit through contacts |20 and |20are broken and contacts |2| and |22 are bridged by the mercury element|20.

If the temperature in the space has not risen to such a high value thatarm |00 has moved into engagement with contact |00, the aforedescrlbedcircuit to the solenoid 00 is' interrupted and this solenoid' istherefore deenergized thus causing the valve 00 to be closed.Refrigerant nowilcws only arm |00, conductor |00, solenoid 60, andconductors |00 and |01 to the line wire 00. Both solenoids are nowenergized so that refrigerant is again supplied to both the evaporatorsand 2| and more sensible cooling in proportion to latent cooling oi theair is efiected sok that the temperature of the air will more rapidly bereduced to the desired value.

Assume now that the temperature of the air is at a desirable value sothat both switch arms |02 l and |00 are out of engagement with theirrespective contacts but the humidity of the air rises to an excessivevalue so that contacts |2| and |22 of the switch |20 are bridged by th'emercury element |20. Current now ilows through the solenoid 0| asfollows: the line wire 00 through conductors |00,` |00, |00, contacts|2| and |22 of the switch |20, conductors |0|, |00, solenoid 0|, andconductors |09 and |01 to the line wire 00. The evaporator coll |2| isnow available for dehumidification of the air although n sensiblecooling is at the time required.

4When coil 2| is being usedfor dehumidicaf tion the temperature of theair leaving the outlet I0 may be'so low as to reduce the temperature ofthe air within the s/pace I0 below a desirable value. A coil |00 isaccordingly placed downstream from the evaporators 20 and 2| and asuitable heating medium is supplied to this coil under the control ofvalve |0I. The stem |02 of the valve |0| may be connected by means of alink |00 to the arm |00 operated by a motor |00 Awhich may be aproportioning motor similar to the motor 00. The operation of this motoris l controlled by a thermostat |10 located in the space I0. Thisthermostat may be similar in construction to thejthermostat 00 and mayinclude bimetallic element '|1| carrying an arm |12 for movementtherewith over resistance |10, the arm |12 and resistance |10 formingthe control potentiometer for the motor |00. Terminals `|10 and |10`ofthe motor are connected by means of conductors |10 and. |11 to theopposite ends of the resistance |10 and the terminal |10 is connected bymeans of conductor |10 to the arm |12 through the bimetallic element|1|. Wires |00 and |0| are provided to supply power to the motor |00.When the temperature of the air is at a high enough value the arm |12 o!the 50 thermostat |10 will be at the extreme right end through theevaporator coil 2 thus causing areduction in the suction pressure in therefrigeration system and therefore a reduction in temperature of thecoil 2|. The greater proportion of the Heat that is removed from the airis now in the form of latent heat so'that the 1temperature and humidityin the space are both reduced. Some of the air passig through thechamber I0 will of course pass over the coil 20 and will not come intocontact l,with the coil 2| so that only a relatively small proportion oithe air is cooled by the evaporators and the air bay-passing theA coil2| may be utilized to reheat the air which is cooled and dehumidied bythe coil 2|'.

Should now the temperature of the air increase l to an excessive degreewhile the humidity in the space is relatively high, the arm |00 will bemoved by the cam |0| into engagement with the contact |00 thus againenergizing the solenoid 00 through the following circuit: from the linewire 00 vthrough conductors |00, |00, `|0|, contact |00,

of resistance |10, and the valve |0| will be closed by the motor |00.Should thetemperature in the space I0 fall below a desired value, arm|12 will move toward the right over the resistance |10 thus causingoperation of the motor |00 and opening of the valve |0| an amountproportional to the reduction in temperature below the desired value. Inthis manner whenever the temperature ci the air is lowered below thedesired value in order to dehumidify the air or for any other reason,the temperature of the air will be again raised by means of ,the coil|00 to the proper value. E E

, It will now be seen that with my system that when the humidity o! theair is sunlci'ently low.

and when the temperature is higher than desirable, refrigerant issupplied to both evaporators 20 and 2|- Should the humidity becomeexcessive, only one evaporator vis used and the temperature in thatevaporator is accordingly reduced -so that dehumidincation of the airaswell as sensible cooling will take place. Upon excessive temperatureconditions refrigerant will be supplied to both coils regardless of thehu- 70 midity in the space in order to secure maximum perature so thatas the outdoor pressure is above a n ltion system including `movingsensible and latent heat from the air t between said latent heat fromair to pair cooling of the air. Also in case the humidity is high andthe temperature is at the proper value, refrigerant will be supplied toone oi thecolls in order to secure dehumidiiication and the all'.if'necessary, will be reheated by means ol.' the coil |60. Thetemperature which will be maintained in the space will .be compensatedby the controller 89 which responds to the outside temtemperature risesa higher indoor temperature will be maintained in order to secureproperconditions of comfort within the space. If desired however this outdoortemperature compensator may be omitted should it be desirable tomaintain the same conditions within the space at all times regardless ofthe outdoor temperature. Thecompressor 22 will be controlled by thesuction pressure and will continue to operate as long as the suctionpredetermined value.

Having described the preferred form of -my invention, many modincationsmay become apparentto those skilled in the art and it should thereforebe understood that my invention is limited only by the scope o1 theappended claims.

I claim as my invention:

1. In an air conditioning system, a refrigeraevaporator means forV rebeconditioned, meam for causinga flow of refrigerant throughsaidevaporator means, means for circulating air past said evaporator ,meansand through a space to be conditioned, dow con trol means forselectively controlling ilow of refrigerant through a portion oi' orthrough all of said evaporator means or preventing ilow of refrigerantthrough any ofV said evaporator means, and means in control ofsald flowcontrol means. said last named means comprising means responsive to thetemperature and humidity of.

said vspace for controlling said now control'means in a manner toprevent iiow of refrigerant to said evaporator means when the spacetemperature and space humidity ilowof refrigerant through all of saidevaporator means when the space temperature increases to a firstpredetermined value and thespace humidity is low, for permitting now ofrefrigerant .through a portion only of said evaporator means wheneverthe space humidity rises to a predetermined value when said spacetemperature is predetermined value and a higher value, and forpermitting ilow oi' refrigerant to all of said evaporator meansregardless of space humidity when the space temperature rises to saidhigher predetermined value.

2. In an air conditioning system, a refrigeration system including areboth low, for permitting `and. humidity is low,

erant into the other evaporator, and temperature and humidity responsivemeans for controlling said iii-st and second valves in a manner to.close both valves when space temperature and humidity are at lowvalues, to open both valves -when space temperature is is at saidintermediate high, and to open both when space temperature value andhumidity is valves regardless of humidity when space temperature risesto a high value.

4. In an air conditioning system, a refrigeration system inclucompressor means and a pair oi' evaporators or removing sensible andlatent heat from air-to be conditioned,l means for circulating air pastsaid evaporators to a space to be conditioned, a rst valve` forcontrolling the flow of refrigerant into one evaporator, a second valvefor controlling the flow of refrigerant into the other evaporator,temperature and humidity responsive means for controlling said rst andsecond valves in a manner to close both valves when space temperatureand humidity are at low values, to open both valves when space tempera-Vture is at said intermediate value and humidityis low, to open only onevalve when space temperature is at an intermediate value and humidity ishigh, and to open botlivalves regardless of humiditywhen spacetemperature rises to a high value, and a suction pressure controller forstart-v ing said compressor vmeans when the suction pressure rises to apredetermined value and forstopping thecompressor means'when the suctionpressure falls to a Vpredetermined lower value. Y

5. In an air conditioning system, a refrigeracompressor means and a pairof evaporators for removing sensibleV and latent heat from air to beconditioned, a first valve for controlling theilow of refrigerant into Yone evaporator, aA second valve for controlling v the flow ofrefrigerant into the other evaporator,

tion system including compressor means and a pair of evaporators for beconditioned, means for said evaporators to a space a ilrst valve forcontrolling circulating all' Past to be conditioned,

the flow of refrigerant into one evaporator, a'

removing sensible andv humidity responsive means for controlling atan.

and humidity is high, and tofirst and second valves,

humidity responsive means-for actuating saidboth of said valves when toarst value and Said.

perature,

vond circuit .means with refrigerant, each means for circulating airpast said evaporators to a space to be conditioned, flrst and secondswitches actuated in sequence upon rising tema humidity actuated switch,and electrical connections between said switchesand said valves forplacing said switches in control of the Same, said electricalconnections forming a flrst circuit means controlled by saidilrsttemperature actuated switch switch `Jfor opening`\ controlled bysaid first and second temperature actuated switches for caus-- saidvalves independently of said humidity actuated switch.

6. An air conditioning system comprising, in combination, a pairofevaporators for removing latent and sensible heat from said air,compresser means for supplying said evaporatorsof said evaporatorshaving a constant superheat expansion valve at the inlet thereof, a rstv alve controlling the flowof refrigerant into one of said evaporators,a second valve controlling the flow of refrigerant into the other ofsaid evaporators, control means for said and temperature and controlmeans to open the temperature rises at an intermediate value to openonly one valve'A and said humidity actuated both of said valves, and asechumidity is low, to close one of said valves when said humidity ishigh as long as the temperature is below a second value higher than saidiirst value, and to reopen said one valve regardless of humidity whenthe temperature reaches said second value. y

'7. An air conditioning system comprising in combination, a pair ofevaporators for removing latent and sensibleheat from said air,compressor means for supplying said evaporators with refrigerant, eachof said evaporators having a constant superheat expansion valve at theinlet thereof, a first valve controlling the Vflow of refrigerant intoone of said evaporators, a second valve controlling the ow ofrefrigerant into the other of said evaporators, control means for saidiirst and second valves, and ltemperature and humidity responsive meansfor actuating said control means to open one of said valves when thehumidity reaches a high value, and to open both of said valves when thetemperature rises to a iirst value and said humidity is low, to closeone of said valves when said humidity is high as long as the temperatureis below a second value higher than said first value, and to reopen saidone valve regardless of humidity when the temperature reaches saidsecond value.

WILLIAM L. MCGRATH.

